autocert support

[dmisol]

Autocert is supported (WSS, DTLS)
Matches comments on PR #867

[davidzhao]

Hi @dmisol, I tested it this and have made a couple of changes. The core change is working well! really impressive that it works automatically

A couple of issues that I still see:

1. TURN/TLS does not work for me. You can test by using the SDK sample app, and selecting Force TURN. Could it be due to NextProtos being set to HTTP 1.1? TURN/TLS would need plain TCP
2. After setting it up, when I visit https://domain with Chrome, it proceeds to give me a ERR_CERT_AUTHORITY_INVALID error. I think this is due to the autocert process.. I'm not sure if there's a way around it. Other browsers accepts the certificate without an issue.

[CLAassistant]

All committers have signed the CLA.